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J. CHEM. RESEARCH (S), 2001 485
J. Chem. Research (S),
2001, 485–487
Interest in the use of microwave irradiation in organic synthe-
sis has been growing in recent years and a number of reviews
have advocated the use of microwave irradiation in organic
reactions.
1,2
Its main advantages derive from almost instanta-
neous ‘in core’heating of material in a homogenous and selec-
tive manner. On the other hand, there are numerous potential
advantages for the use of solid supports in organic synthesis.
3,4
The most important are: improvement in the reactivity of
reagents and in reaction selectivity, reduced pollution and eas-
ier handling and work up. The coupling of these two tech-
niques (microwave and solid support) has attracted much
attention.
5
Fluorescent 1,8-naphthalimide compounds have found
wide applications in a number of areas, outside their tradi-
tional usage as dyes and pigments,
5
including biological
fields
6,7
and polymer science.
8,9
Substituted 7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-
ones (compound P) are usually prepared by two methods.
The first, employs the reaction between naphthalene-1,8-
dicarboxylic anhydride derivatives and appropriately substi-
tuted o-phenylenediamines.
10,11
In the second method, the
reaction between naphthalene-1,8-dicarboxylic anhydrides
and appropriately substituted o-nitroanilines produces an
intermediate-N-substituted-naphthalimide, which, in a second
step, can be converted into the final product by chemical
reduction and condensation.
It has been recognised (in cases where R’=H) that the sec-
ond method utilising o-nitroanilines is superior to the first
method when the corresponding o-phenylenediamine reaction
can and does give two isomers. For example, Okazaki demon-
strated a 63 / 37 ratio of 11- to 10-methoxy and 55/45 ratio of
11- to 10-methyl isomers when 3,4-diaminoanisole and 3,4-
diaminotoluene were reacted respectively with naphthalene-
1,8-dicarboxylic anhydride,
12
whereas pure isomers could be
obtained when the appropriately substituted o-nitroanilines
were first reacted with the anhydride, followed with chemical
reduction and condensation. However, this method yields only
one isomer, is an elaborate synthesis and in the some cases is
unsuitable.
On the other hand, when R = H and R’= substituent group
and the second method is inefficient the use of the first method
usually yields two isomers in approximately similar amounts.
For example, Grayshan and Peters reported a 55.3/44.7 ratio
of 1- to 6-nitro and 63.8/36.2 ratio of 2- to 5-nitro isomers
when 1,2-phenylenediamine was reacted with 2-nitronaphtha-
lene-1,8-dicarboxylic anhydride and 3-nitronaphthalene-1,8-
dicarboxylic anhydride respectively.
10
The formation of the
product takes place through an intermediate aminonaphthal-
imide stage and cyclisation of this compound can be carried
out using each of the two carbonyl groups (Scheme 1).
On agreement with the selectivity of alumina catalysed
organic reactions reported previously, we found that with the
use of acidic alumina and microwave irradiation for the prepa-
ration of fluorescent 1,8-naphthalimides gave a reaction with
high selectivity and yield (Scheme 2).
7H-Benzimidazo-[2,1-a]benz[de]isoquinolin-7-one com-
pounds were simply formed by microwave irradiation of a
mixture of naphthalene-1,8-dicarboxylic anhydride and the
aromatic diamine (1/1) for 7–9 min., followed by isolation and
purification to give the product in more than 90% yield and
with selectivity for one isomer. With this procedure we pre-
pared the parent compound and a series of 7H-benzimidazo-
[2,1-a]benz[de]isoquinolin-7-ones that have a substituent in
the diamine or anhydride ring (Table 1).
In conclusion, fluorescent 1,8-naphthalimide compounds
can be prepared in a mild and selective reaction using acidic
alumina as catalyst and with solid support and microwave irra-
diation.
Experimental
All experiments were carried out in a Westinghouse 1400W (900W
output) continuous wave domestic microwave oven on high power.
The structures of the obtained 1,8-naphthalimides were established
by IR spectroscopic data, melting points and comparison on TLC
plates with samples obntained by literature procedures. Melting
points were determined on a Buchi melting point apparatus and are
uncorrected.
General procedure for the synthesis of fluorescent 1,8-naphthalim-
ides: Naphthalene-1,8-dicarboxylic anhydride (1 mmol), aromatic
SHORT PAPER
Selective preparation of fluorescent 1,8-
naphthalimides using acidic alumina under
microwave irradiation
†
Ali Pourjavadi* and Gholam Bagheri Marandi
Department of Chemistry, Sharif University of Technology, PO Box 11365-9516 Azadi
Ave,Tehran, Iran
7
H
-benzimidazo[2,1-
a
]benz[
de
]isoquinolin-7-one compounds were prepared in a selective manner by reaction
between
o
-phenylenediamines and appropriate 1,8-naphthalenedicarboxylic anhydrides using acidic alumina under
microwave irradiation.
Keywords: fluorescent 1,8-naphthalimides, acidic alumina
* To receive any correspondence. E-mail: AliPourjavadi@iup-ir.com
†
This is a Short Paper, there is therefore no corresponding material in
J Chem. Research (M).
diamine (1 mmol) and acidic alumina (3g-Merck, 1078) were mixed
with grinding. The mixture was irradiated in a 50 ml beaker in a
microwave oven for the times indicated in Table 1. At the end of the
irradiation, the reaction mixture was cooled to room temperature and
extracted with dichloromethane. The extracts were evaporated to dry-
ness and purified by thick layer plate chromatography on silica gel
using hexane/ethylacetate (4/1) as eluent.
Received 20 February 2001; 16 August 2001
Paper 01/762
References
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5 H. Schwander, Ciba-Geigy AG, In. “Ullman’s Encyclopedia of
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604,181.
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9 W. Zhu, Y. Hu, and H. Tian, Synthetic Metals, 2000, 111-112,
477.
10 P.H. Grayshan and A.T. Peters, J. Heterocyclic Chem., 1973, 10,
699.
11 P.H. Grayshan and A.T. Peters, J. Heterocyclic Chem., 1973, 10,
705.
12 M. Okazaki, J. Soc. Org. Synthet. Chem., Japan, 1955, 13, 80 (CA
1957, 51, 2745h).
486 J. CHEM. RESEARCH (S), 2001
Scheme 2
Scheme 1
J. CHEM. RESEARCH (S), 2001 487
Table 1
Entry R
a
R’
b
Irradiation Product Selectivity Yield/% m.p. (Lit.m.p) IR/
time/min /°C /°C cm
–1
, CO
1 H H 9 ______ 95 205–206 (205–206.5)
13
1700
2CH
3
H 9 92 97 214 (212–213)
13
1700
3 OCH
3
H 8 95 92 198–198.5 (197)
12
1698
4 H 2-NO
2
7 93 96 300–301 (298–299)
11
1707
5 H 3-NO
2
7 91 96 312–313 (312–313)
11
1702
6 H 4-NO
2
7 91 96 294–294.5 (294)
11
1705
7 H 3-Br 9 92 95 296–297 (296)
12
1700
8 H 4-Br 9 97 98 224–224.5 (221–223)
12
1700
a
In the case of diamine compound.
b
In the case of anhydride compound.
